Moving logic from Django views to models - django

Question

This is my model:
class Car(models.Model):
make = models.CharField(max_length=30)
model = models.CharField(max_length=30)
rating = models.PositiveIntegerField(validators=[MinValueValidator(1), MaxValueValidator(5)], default=0, blank=True)
avg_rating = models.FloatField(default=0, blank=True)
rates_number = models.IntegerField(default=0, blank=True)
def __str__(self):
return self.make + ' ' + self.model
What's the best way to move the logic from the following perform_create function (in views.py) to my models?
class CarRate(generics.CreateAPIView):
serializer_class = CarRatingSerializer
queryset = Car.objects.all()
def perform_create(self, serializer):
pk = serializer.validated_data['car_id']
rating = serializer.validated_data['rating']
queryset = Car.objects.all()
car_queryset = get_object_or_404(queryset, pk=pk)
if car_queryset.rates_number == 0:
car_queryset.avg_rating = rating
else:
car_queryset.avg_rating = (car_queryset.avg_rating + rating)/2
car_queryset.avg_rating = round(car_queryset.avg_rating, 1)
car_queryset.rates_number = car_queryset.rates_number + 1
car_queryset.save()

Answer 1

It would be much better to create two models. Think about how you are counting average rating. This would be some better idea for now:
class Car(models.Model):
make = models.CharField(max_length=30)
model = models.CharField(max_length=30)
def rates_number(self):
return self.rates.all().count()
def avg_rating(self):
# count average_rating from relation to Rate objects and return it
return average_rating
class CarRate(models.Model):
value = models.PositiveIntegerField(validators=[MinValueValidator(1), MaxValueValidator(5)], default=0, blank=True)
car = models.ForeignKey(Car, on_delete=models.CASCADE, related_name='rates')